A schedule display is a graphic representation on a screen of a collection of schedule data. The schedule data has a process start time, a process end time, a process machine, and other attribute values and it is referred to as a "unit". The specific way to make graphic representations depends on environments, usage, and each user's interest involved. In order to obtain a new display according to such dependency, an existing display program is sequentially modified to create a new display program while viewing the result of each modification. Customization of a display means such modification.
Factors affecting the way in which to make graphic representations are largely divided into two types: those which are associated with each user's view, which are usually determined by each user's interest, and those which are related to detailed graphic object definitions of graphic primitives. In the prior art, there is no available function which enables to modify a schedule display according to the former factors, or in response to a change in a user's view. In order to modify a display on account of the latter factors, on the other hand, some graphic routines of the GKS (Graphical Kernel System (GKS) International Standard (ISO 7942)) and the like are used for programming. This method has been problematic in that it is necessary to locate a part to be modified by checking through a source program inasmuch as it is impossible to find out in advance a suitable program corresponding to a particular graphic representation to be modified. It is none the less impracticable for a user to take the trouble to do so. This method has been problematic also in that a modification in a source program would entail such operations as compilation, which makes it impossible to make any such modification in interactive mode.
The prior patent publications, including JPUPA (Japanese Published Unexamined Patent Application) 61-23003 and PUPA 63-263566 containing references to the prior art pertaining to the preparation and display of schedules with the aid of computers or the like, contain no reference to the modification of a display of schedules according to a view.